Is there something wrong with my tank? Fish dead

[Jake_the_reefer]

So I have had my 20g tank set up for over a year now, all current inverts and fish are doing perfectly fine but the last 2 additions I made both died within 3 days. They are drip acclimated for an hour and temp acclimated. However both fish were rapidly breathing with. I signs of infection, parasites or disease.
Nitrates 3
Phos .01
Nitrites 0
Ammonia 0
Temp 78
Ph 7.9

The only thing going on in my tank is cyano algae but I wouldn't think that would kill them as my other fish are doing great.

The fish were a lawnmower blenny and a yellow wrasse.
My current inhabitants are a clown pair, scooter blenny, hermit crabs, nassarius snails, and Astrea snails

 

[Jake_the_reefer]

The yellow wrasse and lawnmower were different times. Wrasse was a month ago and the blenny was this week

 

[Jake_the_reefer]

Another note, both fish from same store and purchased same day they arrived to the store.